Its a great tub. I'd check into the 860 as it has 3 motors and 10 extra jets *IF* you're really wanting a ton of action at probably not too much of a price increase. But I have the 850's on my floor and in it stacks up well vs equally priced competitors in my market.
I sell South Seas (so yes, I am obviously biased) but for a mid-range price brand I've been happy with the results. My customers tend to enjoy them, they use all Balboa motors and controls, and though I personally have like Waterway Jets for the majority of my career, the CMP jets they use generate a soft massage (low pressure) that some or most brands in the mid range pricing may utilize (high pressure).
I've had a positive experience dealing with Artesian Spas (parent company of South Seas) which is encouraging. The rep and support staff are very quick to respond and have always reimbursed me for any warranty issues. So that is a plus too.
Again- I don't have a dog in this race. I can only tell you of my interaction as a dealer with a manufacturer. Obviously a customer may have a better perspective, one I wish I could relay. But I do hope that this will help you make a decision.
Good luck moving forward.